The present invention relates to a tool for dressing the surface of a petrous (i.e. rocky or stony) material which presents a plane surface, comprising a backplate mounted to rotate on a spindle perpendicular to the said plane face in a plane parallel to that face and furnished underneath with a plurality of cylindrical abrasive rollers of equal diameters, mounted on bearings to be freely rotatable around their principal axes, in a path which is eccentric with respect to the said driving spindle, the arrangement being such that the rollers exibit simultaneously a rolling component and a component of sliding which is tangential with respect to the material.
This type of tool is particularly adapted to equip either a polishing assembly or an automatic polisher designed for dressing, for smoothing and polishing very hard rocks such as granite with the aim of obtaining on them a surface finish sufficient to receive a gloss.